This invention relates to a method of manufacturing a diamond coil for the rotor or stator of a rotating electric machine. More particularly, it relates to a coil manufacturing method which is suitable for automation.
FIG. 1 illustrates a typical diamond coil of the type to which the present invention pertains. As shown in the drawing, a diamond coil usually comprises a plurality of hexagonal strands 1. The two flattened ends of a strand 1 are usually referred to as leads 1a, while the portion at approximately the middle of a strand 1 which is bent in two is called the nose 1d. The sections forming the four sides of the strand 1 adjacent to the leads 1a and the nose 1d are referred to as coil ends 1b, while the sections connecting the coil ends 1b with one another are referred to as straight portions 1c.
A conventional method of manufacturing a diamond coil of the type shown in FIG. 1 consists of bending a plurality of conductors around a special coil form into the shape of a diamond. A coil form 2 used in this conventional method is illustrated in FIG. 2. As shown in FIG. 2, the coil form 2 has a roughly semicylindrical, wooden body to which are secured a nose block 2a and pin 2b for holding the nose 1d of a strand 1, four diagonal blocks 2c which serve as forms for the coil ends 1b, a plurality of holes 2e into which the pin portion of a bending tool 2d is inserted, and two straight blocks 2f which serve as forms for the straight portions 1c of a strand 1.
The process of forming a coil strand 1 using this coil form 2 is as follows. First, a conducting material is cut to a prescribed length and both ends thereof are flattened by rolling, thereby forming a conductor 1e with two leads 1a, as shown in FIG. 3. Next, as shown in FIG. 4, the conductor 1c is bent at approximately its midportion about a round pin 3a which fits into a cap 3b, thereby bending the conductor 1e into roughly the shape of a pine needle and producing a nose 1d. A plurality of identical conductors 1e which were formed in this manner are then combined and mounted on a coil form 2 with their noses 1d inserted into the nose block 2a of the coil form 2 in the manner shown in FIG. 5. The conductors 1e are secured in the coil form 2 by inserting a pin 2b into the nose block 2a so as to pass through the nose 1d of each conductor 1e. The conductors 1e are then divided into two bundles, one of the bundles containing one end of each conductor 1e and the other bundle containing the other end of each conductor 1e. The two bundles of conductors 1e are bent outwards in opposite directions as shown by the arrows in FIG. 5 until they contact the diagonal blocks 2c. At the same time, the bundles are pressed flat against the surface of the coil form 2.
Next, as shown in FIG. 6, a bending tool 2d is inserted into one of the holes 2e so as to grasp one bundle of conductors 1e, and this bundle is bent using the bending tool 2d until it contacts one of the straight blocks 2f. The other bundle is bent in the same manner. The bending tool 2d is then inserted into another hole 2e which is closer to the leads 1a than the previously-described hole 2e, one of the bundles is grasped by the bending tool 2d, and the bundle is bent until it contacts one of the diagonal blocks 2c at the end of the coil form which is remote from the nose block 2a, after which the bundle is pressed against the surface of the coil form 2. The other bundle of conductors 1e is bent in the same manner, after which the conductors 1e appear as shown in FIG. 7. Last, as shown in FIG. 8, each of the leads 1a is bent into a prescribed position using another bending tool 4, and a coil like that shown in FIG. 1 is obtained.
The above-described conventional manufacturing method has a number of drawbacks. First, the dimensions of a coil form 2 are fixed, and a given coil form 2 can be used only for the manufacture of a coil having a certain size. If it is desired to manufacture a coil having slightly different dimensions, a completely different coil form 2 is necessary. Furthermore, it is difficult to achieve good dimensional accuracy with this method. Most importantly, since the coil form 2 has a curved, three-dimensional shape, bending takes place in a large number of planes, making it extremely difficult to perform the above-described bending steps using simple machinery. As a result, only a few of the manufacturing steps have been mechanized, the great majority must be performed by hand, and accordingly this conventional manufacturing method is inefficient.